How can pessimism be minor shirk yet be among the major sins, then be described as reprehensible, and do you mean by that 'kahaahat at-tahreem' (reprehensibility of prohibition)?

The believer who believes that benefit and harm are in the hands of Allah, and that what he considers a bad omen does not affect destiny, and finds fear within himself but it does not deter him from what he intends, then his pessimism is disliked and he must rid his mind of it. As for one who believes in the effect of what he considers a bad omen, his action is considered polytheism (shirk).